Image retrieval techniques are used to help users browse, search, and retrieve images in a large collection of images. Such techniques enable users to search images accessible through the Internet and/or any other collection of images for one or more images that they are seeking. For example, a user may use a search engine to search for images of an object (e.g., a building) or a person (e.g., a celebrity). To this end, a user may input a search query such as “building” or “celebrity” to find the image or images that the user is seeking.
A search engine may identify one or more images in response to a user's search query based on textual annotations associated with the images being searched. In particular, a user's search query may be compared with one or more textual annotations associated with each of the images being searched and search results are presented to the user based on the outcome of the comparison(s). For example, if the user is searching for images by using the search query “building,” a search engine may return images that are annotated with text including the word “building.”
Consequently, the quality of image search results depends on the annotations associated with the images being searched and how such annotations are identified. Some conventional techniques for image annotation involve associating annotations with an image based on data in the document in which that image appears. For example, a search engine may identify annotations for an image appearing in a webpage from information in the web page such as information in the image tag (e.g., title, metadata, etc.) and/or information surrounding the image in the web page.